Composite beam

ABSTRACT

A composite beam is disclosed. The beam includes a beam ( 5 ), a solid slab or a composite slab ( 29 ) positioned on and supported by the beam, the solid slab and the composite slab including a slab section and a plurality of concrete ribs ( 21 ) extending from the slab section. The beam also includes at least one shear connector ( 15 ) positioned in at least one of the concrete ribs and connecting the solid slab or the composite slab to the beam. The beam also includes a reinforcing component ( 19 ) embedded in at least one concrete rib that includes an embedded shear connector or connectors. The reinforcing component is in the form of a mesh that includes line wires ( 41 ) and cross wires ( 43 ) that are connected together at the intersections of the wires.

The present invention relates to composite beams for the constructionindustry.

The term “composite beam” is understood herein to mean: (i) a beam,preferably formed from steel, and (ii) a solid slab or a composite slab;that are interconnected by shear connection to act together to resistaction effects as a single structural member.

The term “shear connection” is understood herein to mean aninterconnection between a beam and a solid slab or a composite slab of acomposite beam which enables the two components to act together as asingle structural member under the action effect of bending which causeslongitudinal shear forces to develop.

In conventional composite beams, typically, the shear connectionincludes shear connectors, slab concrete, and transverse reinforcement.

The term “shear connector” is understood herein to mean a mechanicaldevice attached to a beam (typically to a top flange of the beam) whichforms part of the shear connection.

The present invention relates particularly, although by no meansexclusively, to composite beams of the type which include:

-   -   (a) a horizontal beam (typically steel) supported at each end;    -   (b) a composite slab that is positioned on and supported by the        beam and includes:        -   (i) profiled metal (typically steel) sheeting having a            plurality of pans separated by ribs, the profiled sheeting            being positioned in relation to the beam so that the ribs            are parallel to the longitudinal axis of the beam or the            ribs and the longitudinal axis of the beam describe an acute            angle of less than or equal to 15°;        -   (ii) concrete cast on the sheeting, with the cast concrete            including concrete ribs defined by the pans and sides of            adjacent ribs; and        -   (iii) reinforcement embedded in the cast concrete; and    -   (c) a plurality of shear connectors, typically in the form of        headed studs, embedded in the cast concrete and welded to the        beam thereby to connect the composite slab to the beam.

The present invention is concerned with overcoming a major problem thatoccurs with composite beams of the type described above that includeconventional welded stud shear connectors and profiled steel deckinghaving open metal ribs. The problem is a complex type of longitudinalshear failure involving lateral rib punch-through failure that has beenstudied by the applicant in research work that has been carried out bythe applicant. The problem of lateral rib punch-through is not confinedto this particular type of composite beam.

An object of the present invention is to provide a composite beam withimproved resistance to longitudinal shear failure involving lateral ribpunch-through.

According to the present invention there is provided a composite beamwhich includes:

-   -   (a) a beam;    -   (b) a solid slab or a composite slab positioned on and supported        by the beam, the solid slab and the composite slab including a        slab section and a plurality of concrete ribs extending from the        slab section;    -   (c) at least one shear connector positioned in at least one of        the concrete ribs and connecting the solid slab or the composite        slab to the beam; and    -   (d) a reinforcing component embedded in at least one concrete        rib that includes embedded shear connector or connectors, the        reinforcing component being in the form of a mesh that includes        line wires and cross wires that are connected together at the        intersections of the wires.

The applicant has found that the reinforcing component described insub-paragraph (d) above improves dramatically the resistance to lateralrib punch-through failure of the composite beam.

Preferably the concrete ribs are parallel to the longitudinal axis ofthe beam or the concrete ribs and the longitudinal axis of the beamdescribe an acute angle of less than or equal to 15°.

It is preferred that the mesh be positioned so that the line wiresextend in the longitudinal direction of the concrete rib, ie in thelongitudinal direction of the beam.

With this arrangement, the purpose of the cross wires is to take tensionforces and balance transverse components of shear connector reactiveforces that develop in the base region of the shear connector orconnectors.

The research work carried out by the applicant indicates that lateralrib punch-through failure of the beam would not be prevented withoutthese cross wires.

One purpose of the line wires is to anchor the cross wires so that thecross wires can take tension forces.

Another purpose of the line wires is to balance the longitudinalcomponents of shear connector reactive forces that develop in the baseregion of the shear connector or connectors.

It is preferred that the mesh be positioned in the concrete rib between25% and 75% of the height of the concrete rib.

In a situation in which the composite beam includes a composite slabrather than a solid slab, preferably the composite slab includesprofiled metal sheeting having a plurality of metal pans separated bymetal ribs and concrete cast on the profiled sheeting. With thisarrangement the metal pans and the sides of the metal ribs define theouter surfaces of the concrete ribs.

Preferably the mesh is positioned in the concrete rib below the level ofthe tops of adjacent ribs of the profiled sheeting.

It is preferred that the mesh be positioned in the concrete rib between25% and 75% of the height of the adjacent metal ribs.

It is preferred that the mesh extend across the width of the concreterib at the position of the mesh in the concrete rib.

It is preferred that the reinforcing component further includes aplurality of additional reinforcing elements that extend transverse tothe line wires of the mesh and have one or more than one section out ofthe plane of the mesh.

It is preferred that the additional reinforcing elements be crankedhandlebar-shaped elements.

It is preferred that the section or sections of each additionalreinforcing element that is out of the plane of the mesh extend from theconcrete rib into the slab section of the solid slab on the compositeslab.

It is preferred that the beam be a steel beam.

It is preferred that the profiled metal sheeting be profiled steelsheeting.

It is preferred that the beam be supported at each end.

The beam may be supported also at one or more locations along the lengthof the beam.

The beam may be an internal beam or an edge beam.

It is preferred that there be a plurality of shear connectors.

It is preferred that the shear connectors be headed studs.

The shear connectors may be of any other suitable form such as astructural bolts or channels or shot-fired connectors.

The shear connectors may be arranged in a straight line along the lengthof the beam or may be in a staggered arrangement along the length withsuccessive shear connectors positioned transversely to the precedingconnector.

There may be more than one shear connector at each location along thelength of the beam. For example, the shear connectors may be arranged inpairs along the length of the beam.

It is preferred that there be a minimum spacing between the shearconnectors along the length of the beam of at least 5 times the diameterof the shear connectors.

It is preferred that the spacing between the shear connectors along thelength of the beam be no more than 7.5 times the height of the shearconnectors above the top of the concrete ribs. This maximum spacingavoids having to use a reinforcing component of the type described inAustralian patent application 69998/01 in the name of the applicant inthe composite beam.

In a situation in which the composite beam includes a composite slabrather than a solid slab and the composite slab includes profiled metalsheeting, the top of the concrete ribs is taken to be the top of theadjacent metal ribs.

In one arrangement it is preferred that the reinforcing component be aflat sheet of welded wire mesh that includes a rectangular array ofparallel line wires and cross wires welded together at the intersectionsof the wires.

The present invention is not limited to the arrangement described in thepreceding paragraph and extends, by way of example, to mesh formed fromline wires and cross wires that are welded together at wireintersections and has line wires that have a zig-zag shape along atleast part of the length of the line wires.

The present invention is described further by way of example withreference to the accompanying drawings of which:

FIG. 1 is a perspective view which illustrates, in simplified form, anembodiment of a composite beam (without a layer of concrete that formspart of the beam) in accordance with the present invention;

FIG. 2 is an end elevation of the composite beam shown in FIG. 1 (withthe layer of concrete illustrated in the Figure) in the direction of thearrow A in FIG. 1;

FIG. 3 is a perspective view of the reinforcing component of theembodiment of the composite beam in accordance with the presentinvention that is shown in FIGS. 1 and 2;

FIG. 4 is a graph of connector shear force versus longitudinal slipproduced in research work carried out by the applicant on a compositebeam in accordance with the present invention of the general type shownin FIGS. 1 to 3;

FIG. 5 is an end elevation similar to that of FIG. 2 illustrating aspecific form of the embodiment of the composite beam shown in FIGS. 1to 3; and

FIG. 6 is an end elevation similar to that of FIGS. 2 and 5 illustratinganother embodiment of a composite beam in accordance with the presentinvention.

The embodiment of the composite beam 3 in accordance with the presentinvention that is shown in FIGS. 1 to 3 is in a simplified form toillustrate the composite beam 3 more clearly.

With reference to FIGS. 1 and 2, the composite beam 3 includes:

-   -   (a) a horizontally extending hot-rolled or fabricated steel beam        5 which is supported at each end and at at least one location        along the length of the beam so that the beam extends across        multiple spans between the beam end supports;    -   (b) a composite slab including:        -   (i) profiled steel sheeting 7 in contact with a top flange 9            of the steel beam 5, the sheeting 7 including a plurality of            parallel steel ribs 11 separated by pans 13 and positioned            so that the steel ribs 11 extend in a direction that is            parallel to the longitudinal axis of the beam 5; and        -   (ii) a layer 29 of concrete cast on the sheeting 7 and            having an upper surface 31 (shown in FIG. 2 only), whereby            the metal pans and the angled sides of the steel ribs define            outer surfaces of concrete ribs 21 and the remainder of the            concrete layer 29 defines a slab section of the composite            slab;    -   (c) a plurality of pairs of shear connectors 15 in the form of        headed studs that extend through the particular concrete rib 21        shown in FIGS. 1 and 2 that is positioned on the beam 5 and are        welded to the top flange 9 of the beam 5 at spaced intervals        along the length of the beam 5; and    -   (d) a reinforcing component generally identified by the numeral        19 embedded in the concrete slab in the concrete rib 21 in which        the shear connectors 15 are positioned for preventing lateral        rib punch-through failure of the composite beam 3.

The beam 5, the shear connectors 15, and the composite slab may be ofany suitable dimensions and construction. Typically, the shearconnectors 15 are spaced longitudinally apart by 100-300 mm andtransversely apart by 60-100 mm. Typically, the composite slab has athickness of at least 120 mm.

In addition, whilst the profiled steel sheeting 7 shown in FIGS. 1 and 2has a trapezoidal profile, the sheeting 7 may be dovetail or of anyother suitable shape with open steel ribs.

The reinforcing component 19 shown in FIGS. 1 to 3 is in the form of asteel mesh that is formed from line wires 41 and cross wires 45 that arewelded together at the intersections of the wires to form a generallyrectangular array.

The line wires 41 and the cross wires 45 may be the same or differentdiameters, depending on the circumstances.

The mesh is positioned so that the line wires 41 extend in thelongitudinal direction of the concrete ribs 21 and the cross-wires 45extend transversely to the concrete ribs 21.

In addition, the mesh is positioned within the concrete rib 21 so thatit is below the top of the concrete ribs 21, ie below the tops ofadjacent steel ribs 11, and more particularly in the embodiment shown inFIGS. 1 to 3 is approximately midway between the base of the pan 13 andthe tops of the adjacent ribs 11.

As is indicated above, the applicant has carried out research work on aportion of a composite beam of the type shown in FIGS. 1 to 3 on anexperimental push-out rig of the applicant.

FIG. 4 is a graph of connector shear force versus longitudinal slipproduced in the research work. The applicant determined in comparativetest work that the use of the reinforcing component 19 produced a 64%increase in the strength of the shear connector of the composite beamand also an increase in ductility of the composite beam.

FIG. 5 illustrates a specific form of the embodiment of the compositebeam shown in FIGS. 1 to 3 designed by the applicant for a specificapplication.

FIG. 5 indicates specific dimensions of the composite beam and specificdesign information for the beam.

It is noted that design of the embodiment of the composite beam shown inFIGS. 1 to 3 constructed using grade 500 steel can be based on theinformation in Table 1 below. Stud Longitudinal Cross Wire Cross WireLine Wire Line Wire Spacing s_(c) Diameter Spacing Diameter Spacing (mm)(mm) (mm) (mm) (mm) ≦150 9.5 75 7.6 150 >150 9.5 150 7.6 150

FIG. 6 illustrates another embodiment of a composite beam 3 inaccordance with the invention.

The composite beam 3 has the same basic components as the embodiment ofthe composite beam shown in FIGS. 1 to 3 and 5 and the same referencenumerals are used to describe the same components.

The reinforcing component 19 also includes a plurality of spaced apartadditional reinforcing elements 51.

The additional reinforcing elements 51 are in the form of crankedhandlebar-shaped bars that are tied to the cross wires 45 and extendfrom the rib 21 into the adjoining section of the slab section of theconcrete layer 29 to prevent delamination of the slab at ultimate load.

FIG. 6 illustrates a specific form of the embodiment designed for aspecific application.

In any given situation the number of handlebars can be determined havingregard to factors such as the compressive strength grade of the concreteand the longitudinal spacing of the shear connectors.

Many modifications may be made to the preferred embodiments of thepresent invention as described above without departing from the spiritand scope of the present invention.

By way of example, whilst the embodiment of the composite beam shown inFIGS. 1-3 include pairs of shear connectors 15 along the length of thebeams 5, the present invention is not limited to this arrangement andextends to any suitable arrangements such as arrangements in which thereare single rather than pairs of shear connectors. Such alternativearrangements are shown in FIGS. 5 and 6.

Furthermore, whilst the embodiments are arrangements in which theconcrete ribs 21 are parallel to the longitudinal axis of the beam 5,the present invention is not so limited and extends to arrangements inwhich the concrete ribs 21 and the longitudinal axis describe an acuteangle of 15° or less.

Furthermore, whilst the embodiments are arrangements which include acomposite slab, the present invention is not so limited and extends toarrangements which include solid concrete slabs.

Furthermore, whilst the embodiments are arrangements which include aconcrete rib in which the shear connectors 15 are embedded that isdefined by a pan 13 and adjacent steel ribs 11 of a single profiledsteel sheet, the present invention is not so limited and extends toarrangements in which concrete ribs containing embedded shear connectorsare defined by edge pans and ribs of adjacent split profiled steelsheets.

Furthermore, whilst the embodiment shown in FIG. 6 describes that thecranked handlebar-shaped bars are tied to the cross wires 45, thepresent invention is not so limited and extends to arrangements in whichthe additional reinforcing elements 51 are an integrally formed part ofthe reinforcing component 19.

1. A composite beam which includes: (a) a beam; (b) a solid slab or acomposite slab positioned on and supported by the beam, the solid slaband the composite slab including a slab section and a plurality ofconcrete ribs extending from the slab section; (c) at least one shearconnector positioned in at least one of the concrete ribs and connectingthe solid slab or the composite slab to the beam; and (d) a reinforcingcomponent embedded in at least one concrete rib that includes a saidembedded shear connector or connectors, the reinforcing component beingin the form of a mesh that includes line wires and cross wires that areconnected together at the intersections of the wires.
 2. The compositebeam defined in claim 1 wherein the mesh is positioned so that the linewires extend in the longitudinal direction of the concrete rib, ie inthe longitudinal direction of the beam.
 3. The composite beam defined inclaim 1 wherein the mesh is positioned in the concrete rib between 25%and 75% of the height of the concrete rib.
 4. The composite beam definedin claim 1 wherein, in a situation in which the composite beam includesa composite slab rather than a solid slab, the composite slab includesprofiled metal sheeting having a plurality of metal pans separated bymetal ribs and concrete cast on the profiled sheeting, whereby the metalpans and the metal ribs define an outer surface of the concrete rib. 5.The composite beam defined in claim 4 wherein the mesh is positioned inthe concrete rib below the level of tops of adjacent metal ribs of theprofiled sheeting.
 6. The composite beam defined in claim 5 wherein themesh is positioned in the concrete rib between 25% and 75% of the heightof the adjacent metal ribs.
 7. The composite beam defined in claim 1wherein the mesh extends across the width of the concrete rib at theposition of the mesh in the concrete rib.
 8. The composite beam definedin claim 1 wherein the reinforcing component is a flat sheet of weldedwire mesh that includes a rectangular array of parallel line wires andcross wires welded together at the intersections of the wires.
 9. Thecomposite beam defined in claim 1 wherein the reinforcing component ismesh formed from line wires and cross wires that are welded together atwire intersections and has line wires that have a zig-zag shape along atleast part of the length of the line wires.
 10. The composite beamdefined in claim 1 wherein the reinforcing component further includes aplurality of additional reinforcing elements that extend transverse tothe lines wires of the mesh and have one or more than one section out ofthe plane of the mesh.
 11. The composite beam defined in claim 10wherein the additional reinforcing elements is cranked handlebar-shaped.12. The composite beam defined in claim 10 wherein the section orsections of each additional reinforcing element that is out of the planeof the mesh extends from the concrete rib into the slab section of thesolid slab on the composite slab.
 13. The composite beam defined inclaim 1 wherein there are a plurality of shear connectors in the form ofheaded studs.
 14. The composite beam defined in claim 1 wherein there isa plurality of shear connectors and a minimum spacing between the shearconnectors along the length of the beam of at least 5 times the diameterof the shear connectors.
 15. The composite beam defined in claim 1wherein there is a plurality of shear connectors and the spacing betweenthe shear connectors along the length of the beam is no more than 7.5times the height of the shear connectors above the top of the concreteribs.
 16. (canceled)
 17. A composite beam which includes: (a) a beam;(b) a solid slab or a composite slab positioned on and supported by thebeam, the solid slab and the composite slab including a slab section anda plurality of concrete ribs extending from the slab section; (c) atleast one shear connector positioned in at least one of the concreteribs and connecting the solid slab or the composite slab to the beam;and (d) a reinforcing component embedded in at least one concrete ribthat includes a said embedded shear connector or connectors, thereinforcing component being in the form of a mesh that includes linewires and cross wires that are connected together at the intersectionsof the wires, the mesh being positioned so that the line wires extend inthe longitudinal direction of the concrete rib, ie in the longitudinaldirection of the beam, and the mesh being positioned in the concrete ribbetween 25% and 75% of the height of the concrete rib.